A cold backup, also called an offline backup, is a database backup when the database is offline and thus not accessible for updating. This is the safest way to back up because it avoids the risk of copying data that may be in the process of being updated. However, a cold backup involves downtime because users cannot use the database while it is being backed up.
When system downtime must be minimized, a hot backup can provide an alternative to the cold backup. A hot backup can be done even as users access the database, but some method must be used to ensure that data being updated is noted and can be copied when the update is complete.